In electric vehicles, on-board batteries and fuel cells are put in practical use as energy source. Since the fuel cells are expensive, the on-board batteries are largely used as the energy source of the electric vehicles.
A variety of kinds of on-board batteries mounted on electric vehicles have been proposed (see patent literature 1 (FIGS. 1, 2 and 11)).
As disclosed in JP-B-3683307, a power assisted bicycle includes a battery housing device disposed along a rear surface of a seat tube supporting a seat. The battery housing device has an outer box providing a visual appearance of the device.
As disclosed in JP-B-3683307, an inner box incorporating a battery therein is releasably housed in the outer box. A connection mechanism mates with female terminals to electrically connect the battery to a vehicle-body-side such that electric energy generated by an on-board electric generator is supplied through the connection mechanism to the battery to supply vehicle-body-side parts (an electric motor and on-board electrical components etc.) with an electric power stored in the battery.
An external plug can be inserted into a charge opening of the battery housing device, as needed, to allow an external power supply to charge the battery.
As is clear from the foregoing, the on-board battery is mounted on the vehicle body for the purpose of supplying an electric power to vehicle-body-side parts (an electric motor and electrical components). Apart from supply of a bit of electrical power to the electrical components, however, the on-board battery is not effectively used as the electric vehicle does not travel.
The on-board battery, which is a high-quality electrical storage device, is expected to be utilized as the electric vehicle does not travel.